refactor: more constants, improved types

[bvandercar-vt]

• remove many any types by actually specifying the correct type
• add more constants to CONSTANTS
• improve link between CONSTANTS and types

[archfz]

This looks really good. Nice job.

[archfz]

Should this be merged before the lint update? Thinking of conflicts.

[bvandercar-vt]

This looks really good. Nice job.

Thank you! 😃

Should this be merged before the lint update? Thinking of conflicts.

Either one first is fine. Merge should be easy actually, I can pull from master and do it locally on the branch-- I'll just ignore all the Prettier code changes from that PR (since there are no actual functional code changes, literally just the output of the format script), then re-run the format script after that.